Dolphin calf dies after fishing line tangle in Swan River

An 18-month-old dolphin calf has died a week after its mother, both due to fishing line entanglements in Perth's Swan River.

Wildlife officers retrieved the body of Splash near the Perth Flying Squadron Yacht Club on Monday and her body was taken to Murdoch University for assessment.

She and her mother Highnitch had severe entanglements for several months before their deaths.

Highnitch with one of her calves in the Swan River.Credit:Delphine Chabanne

Highnitch's death

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Earlier this month WAtoday reported government rangers were keeping a close eye on Highnitch and her calf after reports she was entangled in fishing line and also suffering from a skin condition.

On Monday the 14th of August rangers responded to reports from commercial vessel operators at Barrack Street Jetty and Eliabeth Quay and managed to cut part of the line off Highnitch.

But on the Wednesday a member of the public reported a dead dolphin on the Como foreshore and rangers confirmed it was the same dolphin, said Kerry Trayler, estuaries science division head in the Department of Biodiversity Conservation and Attractions.

The entanglement was more severe than rangers had been able to see last week, continuing to Highnitch's tail fin and wrapping around it, and now a plastic bag once used for garden mulch was caught in it.

An ugly death for Highnitch. Credit:DBCA

"We're feeling pretty devastasted. And a little angry," she said.

"That's braided fishing line. Why are people using that kind of fishing line on the river? And that bag, you know, it looks like it just blew from someone's garden."

Dr Trayler said the bag would have acted like a sea anchor, filling with water and weighing down the already struggling dolphin.

She said it was likely the entanglement not only exhausted the dolphin but caused an internal infection by cutting into her. Her immune function would then have been affected, resulting in the outer skin infection that was then made worse by the low-salinity condtions in the waterway.